This following pertains generally to the field of charge pumps and more particularly to high voltage charge pumps for integrated circuits.
Charge pumps use a combination of switches and capacitors to provide a DC output voltage higher or lower than its DC input voltage. To generate the required output, transfer of charge from input to output happens through capacitors and switches. During one clock half cycle, the charging half cycle, the capacitor couples in parallel to the input so as to charge up to the input voltage. During a second half cycle, the boost half cycle, the charged capacitor's bottom plate is boosted with the input voltage so as to provide an output voltage twice the level of the input voltage. This process is illustrated in FIGS. 1A and 1B. In FIG. 1A, the capacitor 5 is arranged in parallel with the input voltage VIN to illustrate the charging half cycle. In FIG. 1B, the charged capacitor 5 is arranged in series with the input voltage to illustrate the transfer half cycle. As seen in FIG. 1B, the positive terminal of the charged capacitor 5 will thus be 2*VIN with respect to ground.
Charge pumps are used in many contexts. For example, they are used as peripheral circuits on flash and other non-volatile memories to generate many of the needed operating voltages, such as sensing, programming or erase voltages, from a lower power supply voltage. A number of charge pump designs, such as conventional Dickson-type pumps, are known in the art. But given the common reliance upon charge pumps, there is an on-going need for improvements in pump design, particularly with respect to trying to save on current consumption and reduce the amount ripple in the output of the pump.